Refrigeration apparatus



Oct. 10, 1961 TARLETON 3,003,684

REFRIGERATION APPARATUS Filed May 29, 1957 4 Sheets-Sheet 1 INVENTOR.FREDERIC L. TARLETON ATTORNEY Oct. 10, 1961 F. L. TARLETON REFRIGERATIONAPPARATUS 4 Sheets-Sheet 2 Filed May 29, 1957 Fig. 3.

INVENTOR. FREDERIC L. TARLETON ATTORNEY Oct. 10, 1961 F. TARLETONREFRIGERATION APPARATUS 4 Sheets-Sheet 3 Filed May 29, 1957 INVENTOR.FREDERIC 1.. TARLETON BY ATTORNEY Oct. 10, 1961 F. L. TARLETONREFRIGERATION APPARATUS 4 Sheets-Sheet 4 Filed May 29, 1957 INVENTOR.FREDERIC L. TARLETON ATTORNEY United States Pater Shine 3,003,684Patented Oct. 10, 1961 3,003,684 REFRIGERATION APPARATUS Frederic L.Tarleton, Oak Park, 111., assignor to General Electric Company, acorporation of New York Filed May 29, 1957, Ser. No. 662,441 7 Claims.(Cl. 230-407) This invention relates to refrigeration apparatus and, inparticular, to a refrigeration compressor of the rotary piston type, inwhich the compressor is housed in a hermetically sealed casing whichforms a part of the low pressure side of the refrigeration system.

In the art, compressors in which the sealed casing is part of the lowpressure refrigeration system are often referred to as low pressurecrankcase compressors. Such compressors have a very substantialadvantage over the high pressure crankcase typein which the casing is apart of the high pressure side of the refrigeration system. Arnong otherthings, charging the system with refrigerant is a much less criticaloperation in the low pressure crankcase system than in the high pressuresystem.

For example, the dichloro-difiuoromethane material sold under thetrademark Freon 12, one of the most commonly used refrigerants indomestic refrigeration, is completely miscible in oil. The crankcasepressure and temperature determine the amount of Freon 12 which can bedissolved in the oil, in accordance with the wellknown laws ofsolubility of gases in liquids. In the low pressure crankcasecompressor, the crankcase pressure is substantially the same as theevaporator pressure. Assuming a conventional domestic electricrefrigeration system, an evaporator temperature of F. corresponds to agas pressure Within the evaporator of pounds per square inch gauge; andit may be assumed that the crankcase pressure is substantially the same.At 15 pounds per square inch gauge pressure, the solubility of Freon 12in the oil is about 3% at an oil temperature of 200 F., and 8% at an oiltemperature of 100 F. These oil temperatures are typical of thoseprevailing at the normal high and low ambient temperatures of domesticrefrigeration operation.

In a high pressure system, in which the compressor discharges into thecasing, the solubility of Freon 12 in the oil may range from 30% to 50%over the same ambient temperature range.

Assuming for purposes of easy example that each refrigeration system(that is to say, the system using a low pressure crankcase compressorand a system using a high pressure crankcase compressor) requires 10ounces of Freon 12 for proper operation, it will be seen that at the lowambient temperature condition, only .8 ounce of refrigerant will bedissolved in the oil in the low pressure crankcase compressor; whereasin the high pressure crankcase compressor 5 ounces will be dissolved. Atthe high ambient temperature, only .3 ounce will be dissolved in the oilin the low pressure compressor; whereas 3 ounces of refrigerant will belost to the refrigeration system in the high pressure crankcasecompressor. In the high pressure crankcase compressor, therefore, if theamount of refrigerant for satisfactory operation is 16 ounces net, theamount charged into the system must allow for the 5 ounces dissolvedinto the oil at low ambient temperatures, and therefore a total of 15ounces must be charged into the system. However, during a subsequenthigh ambient temperature operation, two of those five ounces will leavethe oil, resulting in an overcharge of refrigerant in the system. Suchrefrigerant may flood the evaporator and spill over into the suctiontube, an undesirable condition. On the other hand, if the refrigerationsystem is charged with an amount producing the proper net volumes forhigh ambient temperature operations, the

system will be undercharged for low ambient temperature operations.

In the low crankcase compressor systems, the Variation in the amount ofrefrigerant is only a matter of onehalf of an ounce, and there isneither serious undercharging nor overcharging for proper operationthrough the normal ambient temperature operating range.

These conditions are well known, and apply to both rotary andreciprocating compressors. Rotary compressors have better capacitycharacteristics than reciprocating compressors, in that the rotary losesless capacity at low back pressures; and although the reciprocatingcompressor may have greater capacity than the rotary at high backpressures, the capacity requirement at the least favorable operatingcondition must determine the compressor capacity. Therefore the capacityof the reciprocating compressor must be increased to place it on a parwith the rotary compressor at low back pressures; and such increasegives the compressor an altogether unnecessary capacity at the higherback pressures. The fact remains, however, that although low crankcasepressure reciprocaring compressors are well known in the art, theextreme diihculty of lubricating the piston, eccentric shaft, andcylinder divider blade of a rotary compressor, and of maintaining aproper oil seal between the rotating piston and the cylinder and betweenthe divider blade and the cylinder walls has in the past eifectivelylimited the rotary compressor to the high crankcase pressure type.

The problem which previous workers in the low pressure rotary compressorart had not-been able to solve in a simple and efiective manner is thatof compressor lubrication and sealing. The sealing of the rotary pistonas it traverses the cylinder is entirely by means of an oil film.Although this film is really of microscopic thickness, the total amountof oil used during continuous compressor operation for one hour, even inthe comparatively small size domestic refrigerator compressors, amountsto from twenty to sixty cubic centimeters. This is a substantialquantity and indicates the necessity for having a steady flow oflubricating oil for sealing purposes in addition to that required fornormal lubrication.

In view of its structure and method of operation, the sealing andlubrication of a rotary compressor are directly related to the pressuredifferential between the average cylinder pressure and the crankcasepressure. In a high pressure crankcase rotary compressor, the crankcasepressure is substantially the same as the pressure in the cylinder atthe instant of the discharge of gas therefrom. The average cylinderpressure is, of course, lower than the crankcase pressure. It isaccepted practice to lift oil from the crankcase sump by means of aspiral groove pump on the eccentric shaft. This oil will be at thecrankcase pressure and as it reaches the interface between the rotatingpiston and the bottom end plate of the cylinder, the pressuredifierential will cause some of that oil to flow radially outwardly toseal the interface and to lubricate the relatively rotating parts. Oilwhich continues to travel along the eccentric shaft will enter thesecond interface between the rotating piston and the upper end plate ofthe cylinder, whereupon some of this oil will flow radially outward toseal the upper surface of the roller against gas leakage and also tolubricate the rotor. There is a continuous flow of sealing oil and itwill reach the side wall of the rotor to produce the necessary sealbetween the rotor and the cylinder wall. Oil which reaches the peripheryof the rotor will coat the sliding surfaces of the reciprocating bladewhich in rotary comnressors divides the cylinder into its low pressureand high pressure portions.

These favorable pressure relationships do not prevail in low pressurecrankcase compressors because except for the cylinder portion at theactual inlet thereof, the average cylinder pressure is greater than thecrankcase pressure, and there can be no radially outward fiow of oilfrom the shaft to the periphery of the roller. Obviously, the flow mustbe in the other direction. This pressure relationship introducesproblems not only in the lubrication and sealing of the cylinder wallsand rotary piston, but also in the sealing and lubrication of the blade.

It is, therefore, an object of the invention to provide an improvedmeans for lubricating and sealing the piston and other operatingcomponents of a low pressure crankcase rotary refrigerant compressor.

It is still another object of the invention to provide a low pressurecrankcase type of rotary refrigerant com pressor having means wherebysuficient oil may be introduced into the compressor for lubricating andadequately sealing the relatively moving parts of the compressor withoutthe danger of introducing excessive oil into the refrigeration system.

It is a further object of the invention to provide a low pressurecrankcase type of refrigerant compressor having means whereby compressedgas which may penetrate the oil seal will be returned to the lowpressure side of the cylinder, thus permitting the use of largermanufacturing tolerances without loss of compressor efficiency.

In the attainment of these and other objects, the present inventionprovides for introducing oil into the cylinder at the low pressure areathereof; specifically, a metered amount of oil is brought into thecylinder at a location such that it will coat the periphery of the rotorto seal the cylinderbetween the side wall of the rotor and the cylinderwall and will flow radially inward along the top and bottom faces of therotor to seal the clearance between said faces and the cylinder endplates. Specifically, the inflowing oil is arranged directly to flowupon the upper face of the rotor for radially inward travel between saidupper face and the upper cylinder end plate, and to flow along the sidewall of the rotor. The reciprocating blade is sealed and lubricated byoil which is carried with the compressed gas into a chamber in back ofthe blade. A small quantity of this oil accumulates within this chamberand is distributed over the side walls of the blade by the rapidreciprocation thereof, whereupon all surfaces of the blade become coatedwith a lubricating and sealing oil film.

Although rotary compressors are manufactured to extremely closetolerances, it is good practice to make the tolerances as easy as areconsistent with the necessary tightness against blow-back or otherundesirable pressure. loss conditions within the cylinder. Relaxedtolerances, even though the amount of relaxation is very small, increasethe spaces between the respective piston and cylinder parts and requirea necessarily larger quantity of oil'for sealing. Merely to increase theintroduction of oil into the cylinder would have the adverse effect ofcirculating too much oil within the refrigeration system.

In a presently preferred embodiment of the invention, I provide each ofthe cylinder end plates with a groove concentric with the cylinder andprovide a passage between the groove and the low pressure side of thecylinder. The grooves make it possible to increase the oil needed forsealing and also provide a path whereby high pressure gas which may leakbetween the end plate and the rotor will be returned to the low pressureside of the cylinder. An excess of oil which may reach the grooves willnot be discharged into the refrigerant system with the high pressuregas. The grooves, therefore, permit the increase in the amount of oil inthe cylinder to that necessary to compensate for increased clearancesand thus improve the performance of the compressor.

It must be understood, of course, that the expression excessive oil doesnot infer that oil is introduced into the cylinder in disregard of thebasic consideration that excessive oil is disadvantageous in arefrigeration system. According to the invention, I introduce oil intothe cylinder in a manner in which the piston or rotor acts as a meteringdevice. Therefore the oil inlet passage may be made large enough toinsure a free -flow of oil into the cylinder notwithstanding theextremely low ressure differential between the low pressure portion ofthe cylinder and the crank case.

As will later appear from an inspection of the drawings and descriptionof operation related thereto, the relationship of the oil passage to therotary piston is such that oil is deposited on the outer upper portionof the piston during the greater part of its rotation, and into thecylinder intake portion by flow along the side wall of the piston duringthe instant of lowest cylinder intake pressure. An oil film is thuscreated which spreads through the clearance between the piston and'thecylinder end plates as the cylinder pressure quickly exceeds thecrankcase pressure. This film provides lubrication and sealing. An oilfilm is also established between the adjacent side walls of the cylinderand piston. Although the clearance between the piston and the cylinderside walls is minute, the oil film provides an effective seal.

The cylinder divider blade is in continuous engagemerit with therotating piston and such engagement is maintained by a spring, plus thehigh gas pressure in the chamber which is immediately behind the blade,as previously explained. A portion of the oil-carried about the cylinderon the piston wall is removed from the piston by the blade, and will beconveyed by the high pressure gas into the chamber behind the blade,where it separates from the gas and becomes available for thelubrication and scaling of the blade.

Other features and advantages of the invention will best be understoodby'the following detailed description of a presently preferredembodiment, read in connection with the accompanying drawings in whichFIG. 1 is a side sectional elevation of a refrigerator compressor of therotary piston, low pressure crankcase, type embodying the presentinvention;

FIG. 2 is a transverse sectional view of the compressor looking in thedirection of the arrows 2-2 of FIG. 1 and showing the underside of thecylinder and the rotor;

FIG. 3 is a vertical sectional view of the blade and blade chamber takenon lines 3- 3 of FIG. 2;

FIG. 4 is a transverse sectional view looking in the direction of thearrows 4-4 of HG. l and showing the valve arrangement and the mufllerchambers communicating with the high pressure discharge tube;

FIG. 5 is a transverse section taken on lines 5 S of PEG. showing thedischarge valve communicating between the cylinder and a chamber in thevalve plate;

FIG. 6 is a transverse section taken on lines 66 of PEG. 4, showing thevalve and passages communicating between the blade chamber and the firstmuffler chamber of the valve plate;

FIG. 7 is a bottom plan view taken in section on lines 7-7 of FIG. 1,showing the underside of the frame member;

FIG. 8 is a fragmentary top plan section of the frame member taken onlines 8-8 of FIG. 1;

P16. 9 is an enlarged fragmentary vertical elevation of the framemember, taken on lines 9-9 of FIG. 8;

PEG. 10 is a fragmentary elevation of the frame member in section onlines 1t'P10 of FIG. 7; and

FIG. 11 is a schematic refrigerator circuit diagram.

General description The hermetically sealed, low pressure crankcaserotary compressor 1 is shown in FIG. 11 in its operating environment ina conventional compression-condensationexpansion typerefrigerationsystem. Said system is shown schematically as including a condenser Cconnected directly to the discharge conduit 2 of the compressor andconnected by means including the so-called capillary tubing C to anevaporator E. An expansion occurs when the liquid refrigerant leaves thesmall bore tubing C and enters the substantially larger tubing of theevaporator as is well known in the art. From the evaporator suction tubeE communicates directly with the interior of the hermetic casing 3 ofthe compressor entering said casing by means of a suitable inletconnection 4. The compressor is under the control of a thermostat Thaving suitable switch means in series with the motor of the compressorand a suitable power source. A hermetic electrical connection 5 isprovided at the casing 3. The high pressure side of the refrigerationsystem comprises the discharge portion of the compressor, the condenserG and the capillary tubing C. The low pressure side is represented bythe evaporator E, the suction tube E, the inlet connection 4 and theinterior of the casing 3. In this important aspect, the refrigeratorsystem embodying the present invention differentiates over conventionalhermetically sealed rotary compressor refrigeration systems in which thecompressor casing is an element of the high pressure side of the systemrather than of the low pressure side. It will be understood, of course,that the refrigeration system has been schematically shown and does notinclude certain aspects of the evaporator, such as headers,accumulators, and the like, which are well known in the art.

The compressor 1, FIG. 1, includes a rigid main frame 6 which is securedto the upper part of the hermetic casing 3 and serves to mount thestator 7 of the electric motor. The main frame is formed with a bearing8 which rotatably receives the eccentric shaft 9 of the compressor. Anextension 19 carries the rotor 11 of the motor.

The shaft 9 is formed with an eccentric 12 and an extension 14 which isjournalled in the valve plate 15 and rests upon the thrust plate 16. Thelower portion of the casing 3 may be designated the crankcase and itcontains a substantial quantity of suitable lubricating oil 0, asindicated in FIG. 1. The eccentric shaft 9 is formed with a continuousspiral oil groove 17. The thrust plate 16 has a passage 18 communicatingdirectly with the oil sump and as the shaft rotates, the groove 17 pumpsoil from the sump to a receiver or reservoir of very small capacity, asrepresented by the pocket 19 at the top of bearing 8, the channel 20communicating therewith, and the pocket 59 at the base thereof. It willbe obvious, therefore, that the entire interior of the crankcase 3 is atthe low suction pressure of the refrigeration system and that thelubricating oil being transported by the pumping groove 17 is likewiseat the low pressure. Excess of oil reaching the pocket 59 merely spillsover into the crankcase.

The lower surface 21 of the frame 6 and the upper surface 22 of thevalve plate 15 serve as end plates for the cylinder structure 23confined. therebetween. Said cylinder is formed with a very accuratelymachined cylindrical chamber 24 which is concentric with the motor shaft19 and forms the actual cylinder space Within which operates the rotarypiston or rotor 25. As best a peers in FIG. 2, the piston 25 issubstantially smaller in diameter than the chamber 24 and it is inrotary engagement with the eccentric 12, whereupon as the shaft 10rotates in a counterclockwise direction, as viewed in FIG. 2, the piston25 sweeps or oscillates about the inner wall of the cylinder 23 withvery minute clearance between the otherwise tangential contact of thepiston with the cylinder wall. As shown in FIG. 1, the respectivecomponents are secured together in face-to-face relationship by anysuitable number of fastening means, such as the machine screws 26.

The cylinder is divided into a low pressure side 27 and a high pressureside 28 (FIG. 2) by means of a reciprocating blade 30 which operates ina slot provided for it in the cylinder 23. Immediately behind the blade,the cylinder is formed with a small volume chamber 31 which houses aspring 32. It will be understood that the end pocket 59 will merelyoverflow the rim portion of the blade will enter the chamber 31 duringeach revolution of the piston 25. The blade 30 is maintained in contactwith the wall of the piston 25 by means of the spring 32 and a highpressure gas condition Within the chamber 31, as presently explained.

The low pressure refrigerant vapor which enters the casing by way of theconnection 4 is introduced into the low pressure portion of the cylinderby means comprising an inlet tube 33 which is fitted within an angularlydirected gas intake passage 34 in the frame 6. The passage 34 directlycommunicates. with a substantially semicircular slot 35 provided in thewall of the cylinder, as best shown in FIGS. 1 and 2. As the piston 25rotates in a counterclockwise direction, as viewed in FIG. 2, itcompresses the gas ahead of it; and the compressed gas passes from thehigh pressure portion 28 of the cylinder, through a discharge port 36,and then (see FIGS. -4 and 5) through an opening 37 in the valve plate15, and past the normally closed reed valve 38 into the chamber 39formed by said valve plate and the thrust plate 16. The valve backstop40 stiifens the reed valve 38 and prevents its excessive distortion. Inview of the fact that the chamber 39 is not in communication with any ofthe other chambers in the valve plate, the high pressure gas passesdirectly through a port 41 which registers with a passage 42 extendingthrough a step 43 formed in the chamber 31, as best shown in FIG. 3. Thestep 43 terminates below the frame member 6, and thus provides an alcove44 through which the gas enters the chamber 31. The high pressure gas,therefore, undergoes an abrupt change in its direction of flow as itenters the chamber 31. As presently explained, the gas will contain aquantity of oil, some of which will be separated from the gas by reasonof the abrupt change in direction and will accumulate within the chamber31. The underside of the frame 6 is formed with an elongated passage '45which communicates between the chamber 31 and a passage 46 in thecylinder 23. Passage '45 is, of course, above the chamber 31, and oilwhich was carried by the gas into the chamber 31, therefore, remainswithin the chamber. Passage 46 registers with a passage 47 leading intoa chamber 48 in the valve plate. As best appears in FIG. 6, the passage47 terminates in a valve seat with which cooperates the reed valve 56.It will be noted that said reed valve comprises part of a structureincluding the backstop 51 which, similar to the backstop 40, stifiensthe valve reed and guards it against excessive distortion. The valveplate is subdivided by means of walls, as illustrated in FIG. 4, into aplurality of muflier chambers which are interconnected by means ofvariously arranged passages 52, 53, 54, and 55, which are traversed bythe high pressure gas until it enters the final chamber 56 from whichthe high pressure gas leaves the compressor through the outletconnection 2.

Lubrication and sealing It has previously been noted that rotarycompressors are made to exceedingly fine tolerances and that the minuteclearances between the rotary piston and the cylinder wall and betweenthe piston and the upper and lower end plates thereof are lubricated andsealed by means of a film of lubricating oil.

Pursuant to the present invention, a metered amount of lubricating oil'is introduced from the crankcase into the low pressure portion of thecylinder. Specifically, the lubricating oil inlet port is so locatedthat for at least a large portion of each rotation of the piston, theport will be covered, wholly or in part, by the rotating piston. Asshown in FIG. 9, the oil groove 20 terminates in the preferablyhemispherical pocket 59 having in its botom the oil passage 60. Excessof oil received by the thereof and rejoin the oil in the crankcase. Thepassage 60 enters the cylinder at a location in which the surface of thepiston 25 will sweep across the bottom of the passage. In thisarrangement, the rotating piston exposes a predetermined area of the endof the passage 6t) during a portion of each rotation of the piston; andduring each rotation the periphery of the piston will briefly passbeneath the oil passage, whereupon oil flowing through the passage 66'will coat the side wall of the piston. Because the piston is made andlocated within the cylinder with extreme accuracy, it is used as aprecise valving means to control the inlet of oil. This is veryadvantageous, for the oil passage itself may be made slightly oversizeto insure steady flow of oil under the small pressure differentialexisting in the system, and yet the actual quantity of oil entering thecylinder is accurately metered. The top of the piston continuously wipesa very thin film of oil from the bottom of the oil passage during therotation of the piston. This wiping acton also takes place in varyingdegree as the eccentrically located piston covers and uncovers the oilinlet port.

The efiect of this oil inflow metering operation is to provide an oilfilm between the upper surface of the piston and the bottom of theframe, and an oil film about the wall or" the piston, This latter oilfilm provides the necessary sealing of the piston with respect to thewall of the cylinder. As indicated by the portion 61 in FIG. 2 a slightexcess of oil accumulates ahead of the piston. Some of this excess oil,plus a small quantity of that which is introduced directly into thecylinder from the port 64), will flow between the bottom of the pistonand the upper wall of the valve plate 22. This oil movement must occur,because the cylinder pressure exceeds the crankcase pressure except inthe immediate gas inlet area of the cylinder; in other words, theaverage cylinder pressure is greater than the crankcase pressure, andthe pressure differential will cause a flow of oil toward the crankshaft. A film of oil will also remain on the side wall of the piston.This film forms the seal between the end of the blade 30 and the pistonwall. Oil which may be stripped from the piston wall by the action ofthe blade will be carried with the high pressure gas through the outletport 36. Much of the oil which is entrained in the high pressure gaswill separate therefrom as the gas enters the chamber 31, as previouslystated.

The oil which separates out of the gas in the chamber 31 by reason ofthe abrupt directional change of the gas flow will, of course, tend toaccumulate in the bottom of the chamber because of the elevation of theescape passage 45. Because of the rapid reciprocation of the rearportion of blade 3% within the chamber, and the high gas pressurecondition therein, the blade will be thoroughly lubricated and sealedrelative to the cylinder walls. The

' upper portion of the blade will receive oil by splash lubrication andthe accumulation of oil on the blade as it separates from the oil.Therefore, although one face of the blade within the cylinder is exposedto high pressure, and the other face to low pressure, the combination ofthe high pressure condition and the oil separation within the chamber 31insures proper and thorough lubrication and sealing.

It has previously been stated that it is desirable to makethemanufacturing tolerances as easy as possible without detrimentallyaffecting the seal between the relatively moving parts of the piston andcylinder portions. In order to do this without introducing anundesirable excess of oil into the system, I provide the bottom surfaceof the frame 6 with a circular groove 63, and the upper surface of thevalve plate 15 with a similar circular groove 64. As shown in FIG. 1,the respective grooves are always covered by the adjacent faces of thepiston. Each groove, however, has a branch passage which afiordscommunication from the groove to the low pressure portion of thecylinder. Groove 63 has a passage 65 communicating between grove 63 andgas intake passage 34, as best shown in FIGS. 1 and 7, whereas groove 64has a similar passage 66 as indicated in FIG. 1. Be-

r and below the eccentric.

cause the respective grooves are thus always in communication with thelow pressure side of the cylinder, any excess of oil which may be neededto provide proper sealing for the actual tolerance will always bereturned to the cylinder rather than to the refrigeration system. Thiswould not be true if the excess of oil were permitted to flow to theoutlet port 36 of the compressed gas. By locating the respective groovesat a suitable radius relative to the axis of rotation, an efiective areaof oil seal can be assured. For example, in a small size domesticrefrigeration compressor in which the inside diameter of the cylinder is2.15 inches and the rotary piston diameter is 1.90 inches (thusproducing a pumping stroke of .25 inch) the operational advantages ofthe grooves 63 and 64 have been fully realized by forming the grooves ofv -shaped cross section, .045 Wide, .030" deep, and at a .630 radiusfrom the cylinder axis. The vent passages 65 and 66 may be .125" wideand .030" deep. It will be apparent that the rotary piston sweepseccentrically over the grooves, thus aiding the maintenance of a film ofoil in the radially innermost portions of the piston and cylinder endplates.

Although the illustrated embodiment produces superior results because ofthe oscillation ofthe piston over the grooves and the resultingdistribution of oil throughout the minute space between the piston andthe cylinder end walls, the grooves 63 and 64 may be formed in the facesof the rotary piston, arranged concentrically of the piston on radiiwhich will place the grooves centrally between the inner and outerperipheries of the piston. In this latter arrangement, the bleed-oilchannels 65 and 66 will remain in the cylinder end walls, as previouslydescribed.

The grooves 6'3 and 64, and the therewith cooperating channels 65 and66, prevent high pressure gas and oil from reaching the pumping groove17 on the eccentric shaft, as would be possible if the high pressure gascould flow across the top and bottom of the piston to enter the chambersor pockets 12a and 12b, respectively, above It must be remembered thatthe groove 1'7 is at crankcase pressure, which is considerably lowerthan the average pressure within the cylinder. If high pressure gas werepermitted to flow into the groove 17, the pumping action of said groovewould be interrupted and the compressor starved for oil, with obviouslyobjectionable results. In contrast, the interruption of the flow of oiland gas by the grooves 63 and 64, and the diversion thereofto the lowpressure side of the cylinder, establishes a pressure relationship aboutthe eccentric which is beneficial tothe pumping of oil and thelubrication and sealing of the piston and cylinder in that area. It willbe noted that the upper passage 65 is spaced from the oil inflow port 60by a substantial distance; the pressure existing in the passage 65 isvented through the intake passage 34 and therefore cannot reach the oilinflow port to interfere with the flow of oil into the cylinder.

In contrast to the high-pressure crankcase compressors, in which the hotcompressed gas discharges into the compressor housing, the low gaspressure within the housing of the present invention is relatively cool.This condition simplifies the cooling of the motorcompressor mechanism.

It will be seen, therefore, that the invention provides a low pressurecrankcase rotary piston compressor in which the essential sealing andlubrication of the mechanism is assured.

While there has been described what is at present considered to be thepreferred embodiment of the invention, it will be understood thatvarious modifications may be made therein, and it is intended to coverin the appended claims all such modifications as fall within the scopeof the invention.

I claim:

1. A motor-compressor mechanism comprising a casing havingan inlet forgas to be compressed, a crankcase openly communicating with said casingand containing a quantity of lubricating oil, whereby said crankcase andoil are at substantially the pressure of the incoming gas, a motor and acompressor Within said casing and including a cylinder and an annularrotor therein to provide a rotary piston, said cylinder having endplates overlying the top and bottom surfaces of the piston and a bladeslidably mounted Within said cylinder and engaging the peripheral wallof said piston to divide the cylinder into high and low pressure sides,a shaft driven -by said motor, an eccentric on said shaft in continuousengagement with the inner wall of said piston for oscillating saidpiston about said cylinder in wall to wall tangential relationship, saideccentric shaft being continuously exposed to the pressure conditionWithin said crankcase, means including a pump groove on the exteriorwall of said eccentric shaft and said eccentric and openly communicatingbetween said crankcase and the wall of said piston engaging saideccentric to lubricate said wall, means for intro- 1 ducing apredetermined quantity of oil into said cylinder at the low pressureside thereof during a short interval of each rotation of said piston,whereby the higher average cylinder pressure relative to the crankcasepressure will effect a flow of oil radially inwardly between the pistonand the adjacent surfaces of the cylinder to lubricate and seal thesame, means including a circular passage concentric with said eccentricshaft disposed between the piston and each of the end plates of thecylinder to intercept oil and high pressure gas during the passagethereof toward I said eccentric shaft, passage means in said end platescommunicating between the said circular passages and the low pressureside of the cylinder to conduct thereto the intercepted high pressuregas and oil, and a discharge conduit connected to said compressor andextending through said casing for the discharge of the compressed gas.

2. A motor-compressor mechanism comprising a casing having an inlet forgas to be compressed, a crankcase openly communicating with said casingand containing a quantity of lubricating oil, whereby said crankcase andoil are at substantially the pressure of the incoming gas, a motor and acompressor within said casing, said compressor including a cylinder andan annular piston rotatably confined therein, said cylinder having endplates overlying the top and bottom surfaces of said piston and a bladeslidably mounted within said cylinder and engaging the peripheral Wallof said piston to divide the cylinder into high pressure and lowpressure sides, gas inlet means communicating between the casing and thelow pressure side of said cylinder, a shaft extending through saidcylinder to a position below the level of oil in said crankcase, meansfor rotating said shaft by said motor, an eccentric on said shaftrotatably within said piston in engagement With the wall thereof foroscillating said piston about said cylinder in wall to Wall tangentialrelationship, said eccentric and eccentric shaft having an externalgroove serving to conduct oil from said crankcase to an open receiverWithin said casing above said cylinder, said groove openly traversingthe inner wall of said rotary piston, an oil conduit communicatingbetween said receiver and the low pressure side of said cylinder, saidconduit opening into said cylinder at a location at which said rotarypiston covers at least a substantial portion of said conduit openingduring each rotation of said piston, whereby said piston comprises meansfor metering the flow of oil into said cylinder and the higher averagecylinder pressure relative to the crankcase pressure will effect amovement of oil radially inwardly between the piston and the adjacentsurfaces of the cylinder to seal and lubricate the same, and means forintercepting a portion of the oil and gas in its said radial movementand returning the same to the low pressure side of said cylinder, saidmeans comprising a continuous circular groove formed in each of said endplates and openly facing said piston, said grooves being concentric withsaid cylinder and disposed closer to the eccentric shaft than to thewall of said cylinder and a passage in each of said end platescommunicating between said groove and said low pressure side.

3. A motor-compressor mechanism comprising a casing having an inlet forgas to be compressed, a crankcase openly communicating with said casingand containing a quantity of oil, whereby said crankcase and the oiltherein are at substantially the low pressure of the gas entering saidcasing, a compressor within said casing and including a cylinder and arotary piston therein, a blade slidably mounted within said cylinder andbearing against said piston for dividing said cylinder into low pressureand high pressure portions, means including an eccentric and aneccentric shaft for rotating said piston to cause a wall thereof tosweep about said cylinder in tangential relation therewith, theeccentricity of said piston effecting a reciprocation of said blade, achamber in said cylinder behind said blade and entered by the rearportion of said blade during the reciprocation thereof, a first ductfrom said casing to the low pressure portion of said cylinder, a secondduct from the high pressure portion of said cylinder to said chamber,said second duct eifecting an abrupt change in the direction of flow ofthe gas as it enters said chamber, a third duct opening into saidchamber at a high point thereof and communicating with a high pressuredischarge conduit extending to the exterior of said casing, motor meansWithin said casing for rotating said eccentric shaft, means on saideccentric shaft for conveying the oil from said crankcase to a point ofdischarge Within said casing above said compressor, a small capacityreceiver disposed above said cylinder, said receiver being subject tothe low pressure in said casing, means for conveying the oil from saidpoint of discharge to said receiver, and a passage communicating betweensaid receiver and the low pressure portion of said cylinder, saidpassage entering above said piston at a location where it will bealternately covered and exposed by said piston as said piston rotateseccentrically within said cylinder, whereby the oil is made availableWithin said cylinder for the lubricating and the sealing of said pistonwithin said cylinder by the radially inward flow of the oil induced bythe higher average pressure within said cylinder as respects the lowpressure in said crankcase, and whereby a portion of the oil is alsomoved about said cylinder in advance of said piston by the tangentialrelationship of said piston to said cylinder, so that the oil in saidcylinder is expelled therefrom with the compressed gas through saidfirst duct and enters said chmber behind said blade for the sealing andlubricating of said blade.

4. A motor-compressor mechanism comprising a casing having an inlet forgas to be compressed, a crankcase openly communicating with said casingand containing a quantity of oil, whereby said crankcase and the oiltherein are at substantially the low pressure of the gas entering saidcasing, a compressor within said casing and including a cylinder and arotary piston therein, a blade slidably mounted Within said cylinder andbearing against said piston for dividing said cylinder into low pressureand high pressure portions, means including an eccentric and. aneccentric shaft for rotating said piston to cause a wall thereof tosweep eccentrically about said cylinder in tangential relationtherewith, the eccentricity of said piston effecting a reciprocation ofsaid blade, a chamber in said cylinder behind said blade and entered bythe rear portion of said blade during the reciprocation thereof, a firstduct from said casing to the low pressure portion of said cylinder, asecond duct communicating between the high pressure portion of saidcylinder and said chanrbe a third duct from said chamber communicatingwith a high pressure discharge conduit extending to the exterior of saidcasing, means for rotating said eccentric shaft at high speed, means onsaid eccentric shaft for conveying the oil from said crankcase to asmall capacity receiver disposed above said cylinder, said receiverbeing subject to the low pressure in said casing, a passagecommunicating between said receiver and the low pressure portion of saidcylinder, said passage entering above said piston at a location where itwill be exposed by said piston only as said piston attains a rotationalposition within said cylinder affect-ing minimal pressure with said lowpressure portion thereof, whereby'the oil is made available within saidcylinder for the lubricating and sealing of said piston Within saidcylinder by the radially inward flow of the oil induced by the higheraverage pressure within said cylinder as respects the low pressure insaid crankcase, and whereby a portion of oil is also moved about saidcylinder in advance of said piston by the tangential relationship ofsaid piston and said cylinder and flows with compressed gas into saidchamber behind said blade, and means for separating the oil from the gaswithin said chamber and for accumulating the oil for the sealing andlubricating of said blade.

5. A motor-compressor mechanism comprising a sealed casing having aninlet for gas to be compressed, a crankcase openly communicating withsaid casing, a quantity of lubricating oil in said crankcase, structurewithin said I casing providing a cylinder having upper and lower endplates in covering relationship thereto, an annular rotor of lessdiameter than said cylinder disposed therein in slidaole engagement withsaid end plates, a divider blade slidably mounted in a wall of saidcylinder in slidable engagement with the peripheral wall of said rotorand with the respective end plates, said blade dividing said cylinderinto an intake portion and a compression portion, gas intake meanscommunicating between said casing and said intake portion, dischargemeans for conductslidably mounted in a wall of said cylinder in slidableengagement with the peripheral wall of said rotor and with therespective end plates, said blade dividing said cylinder into an intakeportion and a compression portion, gas intake means communicatingbetween said casing and said intake portion, discharge means forconducting compressed gas from said compression portion to the exteriorof said casing, a drive shaft concentric with said cylinder jo urnalledin said end plates, an eccentric on said shaft disposed rotatablywithin'said rotorto effect a planetating movement of said rotoraboutcsaid cylinder in tangential relation thereto to cause compressionof said gas, a motor for rotating said shaft, a reservoir forlubricating oil within said casing above said upper plate, means on saidshaft and said eccentric in open communication with said crankcase, saidreservoir and said rotor for pumping oil from said crankcase to saidreservoir upon rotation of said shaft, passage means communicatingbetween said reservoir and the intake portion of said cylinder for ingcompressed gas from said compression portion to the exterior of saidcasing, a drive shaft concentric with said cylinder journalled in saidend plates, an eccentric on said shaft disposed rotatably within saidrotor to effect a planetating movement of said rotor about said cylinderin tangential relation thereto to cause compression of said gas, a motorfor rotating said shaft, a reservoir for lubricating oil within saidcasing above said upper plate, means including a groove openlycommunicating with said crankcase and extending spirally around theexterior of said shaft and said eccentric for conducting oil from saidcrankcase to said reservoir upon rotation of said shaft, the groove onsaid eccentric being in direct communication with said rotor and withthe groove on said shaft, passage means communicating between saidreservoir and said cylinder intake portion for introducing oil from saidreservoir onto an end wall of said rotor during the greater portion ofthe planetation thereof, said pas sage means being uncovered by saidrotor only during an instant of lowest pressure within said intakeportion to introduce oil thereinto, whereby upon compression of gaswithin said cylinder the differential between the cylinder pressure andthe crankcase pressure within said oil conducting groove will efiect aradially inward movement of oil along surfaces of said rotor tolubricate and'seal the same relative to said end plates, means includinga passage disposed about said eccentric and between at least one end ofthe rotor and the facing end plate to intercept said oil and any highpressure gas entrained therewith, and passage means toreturn saidintercepted gas and oil to the intake side of said cylinder.

6. A motor-compressor mechanism comprising a sealed casing having aninlet for gas to be compressed, a crankcase openly communicating withsaid casing, a quantity of lubricating oil in said crankcase, structurewithin said casing providing a cylinder having upper and lower endplates in covering relationship thereto, an annular rotor of lessdiameter than said cylinder disposed therein in slidable engagement withsaid end plates, a divider blade gravity flow of oil onto an end wall ofsaid rotor during planetation thereof and to admit oil to said cylinderduring that portion of said planetation efiecting minimal pressurecondition within said intake portion, whereby upon compression of gaswithin said cylinder the differential between the cylinder pressure andthe crankcase pressure will eifect a radially inward movement of oilalong surfaces of said rotor to lubricate and seal the same relative tosaid end plates, and means for interrupting said oil movement after ithas traversed substantially the entire radial dimension of said rotorand for returning oil and any high pressure gas entrained therewith tothe intake side of said cylinder.

7. Refrigerating apparatus comprising a casing having an inlet forgaseous refrigerant to be compressed, said casing having a crankcaseopenly communicating therewith for containing a quantity of lubricatingoil, whereby the gaseous refrigerant and the lubricating oil are atsubstantially the same low casing pressure, a refrigerant compressorarranged in said casing and having a cylinder, upper and lower wallmembers in covering relation to said cylinder for sealing the same, anintake passage openly communicating between said casing and saidcylinder for the admission of gaseous refrigerant at low casing pressurefrom said casing into said cylinder, 2. valved discharge passagecommunicating between saidcylinder and the exterior of said casing, arotary piston of smaller diameter than said cylinder disposed in saidcylinder, motor driven shaft means rotatably mounted in concentricrelation to said cylinder, an eccentric on said shaft means in drivingrelation to said piston for rotating said piston within said cylinder ina planetating manner in which said piston and said cylinder are intangential relationship with minute clearance with respect to therespective facing walls of said piston and cylinder, divider meansdisposed in a Wall of said cylinder between said intake and dischargepassages and continuously engaging said piston to establish highpressure and low pressure portions of said cylinder, pumprmeans suppliedwith lubricating oil from said crankcase for affecting a continuous flowof lubricating oil to a receiver of small capacity relative to saidcylinder, said receiver being wholly above said cylinder and thelubricating oil level in said crankcase, whereby the lubricating oil insaid receiver is exposed to the pressure within said casing, saidreceiver having anoverflow rim externally of said cylinder and in closevertical proximity to the. interior thereof, and a passage through theupper covering wall of said cylinder for conducting lubricating oil fromsaid receiver to the low pressure portion of said cylinder, said pistonbeing in covering relation to said passage except for that portion ofthe planetation of said piston deriving minimum pressure within said lowpressure portion of the cylinder.

(References on following page) UNITED STATES PATENTS Badger Oct. 16,1934 Richard Apr. 21, 1936 5 Tarleton Dec. 20, 1938 Hubacker Dec. 29,1942 14 Berry Mar. 20, 1951 Daniel Dec. 30, 1952 Makarofi June 30, 1953-Flame et a1. July 26, 1955 Dill Oct. 18, 1955 Rusch Oct. 16, 1956

